Reply 180 of 253, by eeguru
I recently took detailed measurements from a number of sounds cards to get the WB footprint correct. It seemed like everything was snapped to an imperial grid. I arrived at the same 5050 x 3100 mil hole differences as Tiido with the same 250 mil offset to pin 1. Those translate to the same mm dimensions as above. It was refreshing to convert my part footprint to millimeters and see the same numbers on his drawing. Thanks for that.
It really doesn't matter where you center the WB card itself as long as you have room for the standoffs to land free of traces and the board edges to clear tall components, etc.
I do plan on adding a 10 pin additional header to my footprint to allow for ID of newer WB cards (I2C) and passing of digital audio (I2S) back from the Ext.WB cards to my current sound card project. Of course any older daughter card would still use the legacy 26-pin header. But I am designing a WB daughterboard that will accept a Raspberry Pi Compute Module 3 (CM3) to provide MUNT emulation true'r to MT-32 and the like. I figured having a digital audio output option in 2019 would be ideal. Maybe we can all adopt it as a standard? I've also added an intermediate mounting hole so shorter cards (like the CM3 Pi) can have more than one support boss. I thought about adding a support for Dreamblaster X2 proprietary hole, but my card already has one-integrated on-board and I'm running short on PCB space.